There is a need to print metallized patterns of gold or silver on substrates, such as webs of paper, foils laminated to paper, and films. Metallized ink has been used to accomplish this by utilizing a conventional ink printing press. However, metallized ink lacks the lustre of other metallized sources, such as roll leaf. Thus, it has become necessary to use the roll leaf transfer techniques discussed below to create more desirable metallized patterns on such substrates.
Roll leaf is a very thin, laminated product with an outer transparent polyester film carrier which has a release coat made from wax, filicone or resins. Next, a colored or clear lacquer is applied to the release coat, followed by an application of a vacuum metallized layer. The last layer is a size coat or primer which functions to protect the metallized layer and as an adhesive during a transfer operation. Roll leaf is, in effect, colored foil.
A common technique for applying roll leaf involves feeding it into an apparatus which is in the form of a press having a steel plate adapted to transfer the colored foil to a substrate by way of pressure and heat The colored foil is placed over a surface to which it is to be applied, a heated platen with a die consisting of the design to be applied is pressed onto the foil, and the impact of the die transfers the foil to the substrate on only those portions of the foil where the die has been applied. This technique is commonly referred to as "hot stamping".
Many commercial products are typically provided with multi-colored decorations or labeling in an effort to catch the eye of a consumer. Because metallic colon afford a stylish, if not expensive, look, it is common practice to provide multi-colored decorations and labeling with metallic colon as well as with non-metallic colon. In the past, such multi-colored decorations and labeling have been produced using a hybrid process consisting of a conventional printing operation, utilized to apply a non-metallic ink, and a conventional hot stamping operation, utilized to apply metallic foil. Because the hot stamping operation is carried out separate from the printing operation, the hybrid process is not performed in an in-line manner. As a result, normal priming press operating speeds must be significantly reduced in order to accommodate the slower throughput rates of standard hot stamping machines, whereby the overall processing time is increased and the overall production rate is decreased. Rotary hot presses have been developed which can be operated in line with a conventional printing operation. While eliminating the intermittent operating pauses associated with the use of conventional non-rotary hot stamping machines, these rotary hot presses operate at line speeds which are slower than those of conventional printing operations, whereby the overall processing time is still increased and the overall production rate is still decreased. Rotary hot presses are also disadvantageous because they require the use of heat and they are expensive.
In addition to the stamping methods described above, various cold-foil transfer methods have been proposed. These methods are not, however, carried out in-line on an otherwise conventional printing press. Rather, known cold-foil trier methods have made use of high pressure presses and drums (see U.S. Pat. No. 4,484,970); a two-step manual foil applying process (see U.S. Pat. No. 4,994,131); and a xerographic process (see U.S. Pat. No. 4,868,049).